Indexed language

About: Indexed language is a research topic. Over the lifetime, 334 publications have been published within this topic receiving 11000 citations.

Recursive generation of local adjunct languages

Abstract: The local adjunct grammars and languages have been introduced by Joshi, Kosaraju, and Yamada in response to linguistic considerations. These grammars differ fundamentally from the Chomsky phrase-structure grammars, and they generate a distinct class of languages.

Automata-based parsing in dynamic programming for linear indexed grammars

Abstract: A general framework for the development of parsing algorithms in dynamic programming for Linear Indexed Grammars (LIG) is derived from the concept of Logic Push-down Automata (LPDA), an operational device for the construction of parsers for logic grammars. By exploiting several properties of the LIG formalism, we can guarantee both termination and completeness, which is not possible in the general case of logic grammars. In this paper we center our attention on the class of weakly predictive parsing strategies, which include bottom-up algorithms. The interpretation in dynamic programming of parsing algorithms belonging to this class can be performed in O(n) complexity, which is the lower bound achieved for LIG. In this context, a version for LIG of the LR parsing strategy is developed. The results are also applicable to other automata-based strategies, such as Left Corner.

Left-most derivation and shadow-pushdown automata for context-sensitive languages

Abstract: In this paper left-most derivation for context-sensitive grammars is presented based on Penttonen one-sided normal-form. The derivations using grammars in normal form are represented by tree-like graphs. Left-most derivation is defined in the sense of constructing the derivation graph. The concept of the well-known pushdown automata is generalised. A special-type of automata, the so-called shadow-pushdown automata are presented. The work of the automata is based on the left-most derivation of context-sensitive languages. The class of shadow-pushdown automata characterizes exactly the context-sensitive languages.

Non-self-embedding linear context-free tree grammars generate regular tree languages

Abstract: For the class of linear context-free tree grammars, we define a decidable property called self-embedding. We prove that each non-self-embedding grammar in this class generates a regular tree language and show how to construct the equivalent regular tree grammar.

Mildly context-sensitive languages via buffer augmented pregroup grammars

Abstract: A family of languages is called mildly context-sensitive if - it includes the family of all e-free context-free languages; - it contains the languages • {anbncn : n ≥ 1} - multiple agreement, • {ambncmdn : m, n ≥ 1} - crossed dependencies, and • {ww : w ∈ Σ+} - reduplication; - all its languages are semi-linear; and - their membership problem is decidable in polynomial time. In our paper we introduce a new model of computation called buffer augmented pregroup grammars that defines a family of mildly contextsensitive languages. This model of computation is an extension of Lambek pregroup grammars with a variable symbol - the (buffer) and is allowed to make an arbitrary substitution from the original pregroup to the variable. This increases the pregroup grammar generation power, but still retains the desired properties of mildly context-sensitive languages such as semi-linearity and polynomial parsing. We establish a strict hierarchy within the family of mildly context-sensitive languages defined by buffer augmented pregroup grammars. In this hierarchy, the hierarchy level of the family language depends on the allowed number of occurrences of the variable in lexical category assignments.